Hydrocracking process



1965 R. H. KOZLOWSKI ETAL 3,184,402

HYDROCRACKING PROCESS 2/ M, 0333 A TORNEYS May 18, 1965 Filed April 8, 1964 VOLUME PERCENT YIELD OVERHEAD TEMPERATUREFZ R. KOZLOWSKI ETAL 3,184402 HYDROCRACKING PROCESS 3 Sheets-Sheet 2 FIRST ZONE SECOND ZONE\ PNAPHTHA PRODUCT SYNTHETIC MIDDLE DISTILLATE PRODUCT 500 (FEEDI IBP) FIG.2

CATAL.YST= Ni M ON ALUMINA,

SULFIDED HYDROCRACKING conomons:

800 F. 1200 PSIG 0.1 LHSV NITROGEN. PPM:

FEED. 1700 PRODUCT. 12

FEED: BOTTOM 55 V01..%

' OF A MINAS CRUDE 0 I I I I I I I I I I VOLUME PERCENT OVERHEAD INVENTORS ROBERT H. KOZLOWSK/ NORMAN J. PA TERSON JOHN W. SCOTT, J/.

Unted States Patent 3184,402 HYDROCRACKHNG PRCESS Robert I-I. Kozlowski, Berkeley, Norman J. Paterson, San Rafael, and John W. Scott, .r., Ross, Caiif. assignors to Caiifomia Research Corporation, San Francisco,

Calif., a corporation of Delaware Filed Apr. 8, 1964, Set. No. 359,548 4 Claims. (Cl. 208-59) INTRODUCTION This applcation is a continuation-in-part of appiication Serial No. 113,759, filed M-ay 31, 1961, now abandoned.

This invention relates to a hydrocarbon conversion process, more particularly to a hydrocarbon conversion process for converting petroleum distillates and residua to various valuable products, and, still more particulariy, to a flexible staged catalytic conversion process capable of producing both gasoline and middle distiliates in widely varying ratios to meet dernand fluctuations resultng trom seasonal or other causes.

PRIOR ART PROBLEMS AND SOLUTIONS It has been well known heretofore that seasonal fluctuations exert a heavy influence on the ratio of gasoline and rniddle distillates that retiners are called upon to produce. Further, particularly in recent years in which the supples of orude have been adequate or in excess of needs in most areas, there has been an incentive for increasing the ratio of middle distillates to gasoline; particularly, this incentive has been heightened by jet fuel requirements and by the lack of neecl in certain foreign crude producing areas for large quantities of gasoline.

Even though a refiner increases the ratio of middie distillates to gasoline production in response to factors such as the foregoing, there are other factors, particularly seasonal changes, that frequentiy requre him to reverse this trend to decrease the ratio of middle distillates to gasoline producton. Accordingly, a refiner is interested in a high degree of flexibility in order to show the required changes in these ratios promptly as the need arises. Conventionally, a refiner obtains the desired degree of flexibility by proper manipulation of the various feed strearns and products from a large number of conversion processes including thermal cracking, cataiytic craci ing, hydroeracking, coking and reforming. However, it is obvious that manipulation of the feed or product Ielated to any one such unit in an interrelated system of units Will necessarily require careful consideration of the effect on the -other units. Accordingly, a most desirabie objective is the attainment of the highest degree of flexibility in products produced, with the minimum number of conversion units. Heretofore, such fiexibility, particularly in obtaining widely varying ratios of middle distiilates to gasoline production, has not been obtainabie as a practical matter with a single or two-stage hydrocracking process.

OBJECTS In view of the foregoing, it is a primary object of the present invention to provide a two-stage hydrocracking process capable of producing wide1y varyng ratios of middle =distillates t-o gasoline in response to the effects on iemand of seasonal or other changes.

THE PRESENT INVENTON In accordance with the present invention, there is pro vided a two-stage hydrocarbon conversion process wherein catalysts of difierent acidities are used in the two stages and wherein Wide variations in the ratio of middle distillates to gasoline produced -are obtained by interstage fractionation and proper manipulation of operating conditions, fractionation cut points, and recycle streams.

More particularly, in acco-rdance With the present invention there is provided a process for converting a hydrocarbon feed selected from the group consisting of hydro carbon distillates boiling firom about 500 to 1100 F. and hydrocarbon residua boiling above about 1050 F. which comprises conve-rting in a first conversion zone from 10 to 50 volume percent of said feed per pass to fractions boiiing below the initial boiling point of said feed, said first zone being operated at about 550 to 900 F. a space velocity of trom about 0.1 to 3.0, and a hydrogen partial pressure of 500 to 3000 p.s.i.g with a catalyst comprisng a hydrogenating-dehydrogenating component and a cracking component having no more than weak acidity, withdrawing reaction products f-rom said first zone, separating said reaction products in a ractionating zone to produce at least one bottoms fraction boiiing above 320 F. and a naphtha fraction boiling below 400" F., withdrawing said naphtha fraction from the system as a product, passing at least a portion of sad bottorns fraction to a second conversion zone, ccnverting in said second zone at least 20 volume percent of said portion per pass to products boiling below the initiai boiling point of said portion, said second zone being operated at about 450 to 850 F., a space velocity of trom about 0.2 te 5.0, and a hydrogen par-tial pressure of at least 350 p.s.i.g., wtih a catalyst comprising a hydrogenatingdehydrogenating component and an active, strongiy acid cracking component, withdrawing an efiiuent f-rom said second zone, and recovering desired products from said efiuent.

DRAWINGS The novel features of the present iuVen-tion are set forth with particularity in the appended claims. The invention will best be understood and additional objects and advantages thereof will be apparent from the following description of an exempiary process for producing middle distillates, gasoline and other products trom petroleum distillzrte and residua feed and for achieving wide variations in the middie distillates-to-gasolne ratio, whe-n read in connection with the accompanying drawings, in Which:

FIGURE 1 is a flow diagram illustrating a preferred arrangement of process units and flow paths for use in practicing the present invention;

FIGURE 2 is a graphical qualitative representation of the diiferences in product distribution obtained with the different catalysts in the two conversion zones in the process of the present invention;

FIGURE 3 is a graphical representation of the product distribution obtained when hydrocracking a specific feed stock in the presence of a representative catalyst used in the first stage of the process of the present invention;

F1GURE 4 is a graphical representation of the efect of the feed boiling range on the percent cracking conversion in the first stage of the process of the present invention.

OVERALL Pnociss Referring novv to FIGURE 1, there shown is an exemfirst conversion zoneis conce1itrated in the middle distilplary overall process flow diagram suitablefor carrying out the process of the present invention.

The hydrocrbon feed to be converted is passed thfough line 1 into first converion zone 2, where it is hydrocracked and, if it contains nitrogen, also is at leastparti-ally denitrified. The feed may be any petroleum distillate boil ing within a range of 500 to 1100 F. and any petroleum resduum boiling above 1050 F. or mixtures thereof.

Satisfactory feed stocks nclude heavy gas oils and catalytic cycle oils, conventional 650 to 1050 F. FCC

-feed stocks, and the 650 to 850 F. portioh of such FCC feed stocks. Frst conversion zone 2 is discussed in detail below. Hydrogen for the hydrocrac-king and any denitrification reactionsin zone 2 is supplied to that zone through line 3. Conversion products from zone 2 are withdravvn through line 4 where theyare contacted in high pressure separator5 with Water supplied through line6. From high pressure separator 5 a hydrogen stream is recycled through line 7 From high pressure 'separator 5 conversion products are passed to low pressure separator 8, -froin which water is -re1hoved t-hr-ough line 9. A gas strearh is separated through line 10 trom the conversin prbducts iriseparator 8, and the remainder of the conversion products are passed through line tosclistillation column 16.

From distillation column 16 a gas streamis withclraivn through line 17, and anaphtha stream is removed from the system through line 18, either as a product or for further processing, for examplein a 'reforming zone. A

stream is passed from column 16 through at least one of lines 19, 20 and 21 toline 22 and thence to second conversion zone 23. Jet fuel and middle distillate products may be withdrawn through lines 24 and 25, respectively. A stream may be recycled through lines 30 and 31 and may be a. bottoms stream;remainirig after streams are wthdrawn trom column 16 through lines 19 and/ or 20 and/01121. or, if all but one of lines 19, 20 and 21 are closed, may nclude the streams that otherwise would have passed through these closed lines. For further flexibility, a middle distillate stream mayberecycled late range, whereas the product from the second conversion zone is spread more evenly over the whole boiling range below the initial boiling point of the feed, with a large yield in the naphtha range. The reason for these dierencs in product distribution are disoussed in the detailed discussion below relating to the first and second conversion zones, respectively. These differences are drawn upon as one of the main bases for the remarkable flexibility of the process of the present .invention for producing middle distillates and gasoline in vvidely varying ratios.

FEED T Oi FIRST CQNVERSION ZONE As discussed above in connection with the detailed descriptori of FIGURE 1, the feed to the first conversion zone may be any petroleum distilla te boiling 'from 500 to 1100 F. any petroleum resid1iurn boiling above 1050 F., and mixtures threof. -Heavy gas oils and catalytic cyclefloils are excellentfeeds to the process, as well as conventinal FCC feeds and portions thereof. Residua low in normal parafins (therefore having low fr eezing points); Where the feed has an initial.hoiling point above 500 F., it may be converted in. the first conversion zone directly to a synthetic material (i.e. one boiling below the feed initial boiling point), which is a preferred jet fuel having a high naphthene content, low normal paraflin contentand therefore lowfreeze point, and low aromatijcs 'contentandtherefore acceptably high smoke point. Ithas been found .thatfeeds having lower initial boiling points,for exan1ple around 400 F., tend to pro- -duce excessive quantities of non-synthetic products having a high aromatics content and therefore an unacceptably lowsmoke point, although the freezepoint-may be satisthroughline 32, for example"whereit is desired to close line 30 and recycle middledistillate only to first conversion zone 2. A net product stream may be removed through line 33 and may be further processed if desired, for example, by being sent to acatalytc cracking zone.

The feed entering second conversion zone 23 through line 22 is converted there in the presence of hydrogen supplied through line 34. Secondeonversion zone 23 is discussed in detail below. The efliuent fromsecond conversion zone 23 is withdrawn through line 35 and passed to high pressure Separator 36 from which a hydrogen stream is recycled through line 40. The conversion products from high pressure separator 3 6 are passed through line 41 to low pressure separator 42frorn which a gas stream isremoved through line 43. The conversion products remaining in low pressure separator 42 are passed through line 44 to distillation column 45, From distillation column 45 a naphtha strem is withdrawn from the system throughline 46 for use as a product or for further processing,ior example by reforming. A jet fuel stream may be withdrawn through line 47 and a middle distilla te stream may he withdrawn through line 48 or either or both of these streams may be combin ed with the bottoms stream that may be recycled through line 22.

A net bottoms strem may be withdrawn through line 49 and, if desired, may be passed to a catalytic crackii1g zone for further conversion.

Referringnow to FIGURE 2, there shown is a qualitative graphical representation of the differences in product distribution betweentheproducts of the first and.

factory. 'Such non-syi1thetic product also tends tohave a highpour point.

The nitrogen content of the feedto the first conversion zone is; dependent upon the nitrogen content requirements of the feed to the second conversion zone. The nitrogen.

content of the feed to the second Zone generally should be below 1000 parts per million, preferably below:l00 parts per million, and still more preferably below 10 parts per million. The nitrgen content of the feed to the first conversion zone can be ar1ything consistent with these requirerhents. However it should be noted in connection with high nitrogen-coirtent eeds that, even 'though the first conversionzone could be operated to reduce the m'- trogen content to some minimum level without exceeding the permissible limit of cracking;sevefity it may be fiound very desirable not to accornplish this much denitrification, but rather to accomplish some lesser amount and permit the excess nitrogen to pass thrbugh to the second conversion zone. This method of operation will require an 1ncrease ll'l pressure in the second conversion zone;

however, particularly with heavy feeds, it will frequently permit a much greater decrease in pressure in the first conversion zone. A most desirable Objective is to operate both of the zones at substantilly the same pressure, Because pressure is nitrogeh-dependent, this type of operation may be facilitated by controlling the ainountof ni trogen passing tothe second conversion zone and where necessary, deliberately permittirig nitrogen to pass to that zone. This method of handling the nitrogen contents of second conversion zones of the process of the present inventon. It will be noted that the product from the the feeds to the two zonesis applicable even in the ab sence of the interstagefracitionation which is anessential feature of the present invention. The catalyst used in the first conversion zone generally hasa high degree of denitrfication activity and accordingly where nitrogen-containing feeds are supplied to the process the first conversion zone will accomplish a substantial amount of denitrification concurrently with the hydrocracking in that zone.

FIRST CONVERSION ZONE The first conversion zone in the process of the present nvention produces a high quality product that has a low sulfur content, that has a high degree of saturation and therefore good burning qualites, and that is stable to oxidation and storage. The approprate portions of the product have utility as superior heating oils, diesel fuels and jet fuels.

In the first conversion zone conditions are used in conjunction with the first zone catalyst that are only severe enough to convert naphthenes and aromatics, but not severe enough to crack substantial quantities of paraflins. A desired objective is to crack only the naphthenes boiling above the middle distillate range and to conserve the naphthenes boilng in the middle distillate boilng range. Ths objective is acheved with ease in the present process and the product from the first conversion zone in the middle distillate range is highly naphthenic and therefore very desirable for middle distillate uses requiring a low freeze point, low pour point, high cetane number, good heating value and/or comparatively high smoke point.

The catalyst in the first conversion zone, which as discussed below must be non-acidic or snbstantially nonacidic, must be a hydrocracking catalyst that is capable of converting the feed at a per-pass conversion of from to 50 volume percent of said feed, under the operating conditions in the first zone in large part to reacton products in the synthetic mddle distillate boilng range, i.e., products boilng not only in the middle distillate boilng range but also be1ow the initial boilng point of the feed.

It has been found that a non-acidic or substantially nonacidic catalyst capable of accomplishing the foregong conversion must comprise a hydrogenating-dehydrogenating component, alone or together with a separate cracking component, comprising at least one metal, metal oxide, metal sulfide, metal selenide or combnation thereof, preferably oxides and sulfides of metals of both Groups VI and VIII of the Periodic Table. The most preferred catalyst will comprise combnations of sulfides of cobalt and/ or nickel with sulfides of molybdenum and/ or tungsten. Examples are nickel sulfide and molybdenum sulfide together with alumina, nickel sulfide and tungsten sulfide together with a cracking component that does not have strong acidity. Tungsten sulfide alone is inoperable because it is known to be strongly acidic when 110t modified by other components.

The aforesad non-acidic or substantially non-acidic catalyst generally will comprise the aforesaid hydrogenating-dehydrogenating component assocated with a separate cracking component. It is essential to the process of the present invention, where a separate cracking component is used, that it be snhstantially non-acidic, or at the most only weakly acidic. Exemplary cracking components include silica, charcoal, kieselguhr, titania, zirconia, bauxite and alumina, with alumina being especially preferred. While alumina sometimes is considered to be weakly acidic, its acidity is so 1ow compared with silicaalumina for example, that it may be considered for purposes of the present process to be non-acidic, particularly in view of the markedly different product distribution it provides as compared with a silica-alumina support. For purposes of the present process, the cracking component particularly cannot be a strongly acdic mixed oxide, such as the well-known silica-alumina support conventionally used in hydrocracking catalysts and used as such as a catalytic cracking catalyst.

An outstanding catalyst composite fulfillng the aforesaid requirements both as to hydrogenating-dehydrogenating component and cracking component is a snlfided catalyst comprising 4 to 10 weight percent nickel, as

metal, and 15.5 to 30 weight percent molybdenum, as metal, and a substantially non-acidic base consisting essentially of alumina. The preferred method of preparing the catalyst is by impregnating the cracking component in a solution of the hydrogenating-dehydrogenatng component. However, catalysts prepared by various types of cogeilation procedures are fully operable.

The aforesaid catalyst combination results in a significantly different product dstribution from that obtained with acidic-type hydrocracking catalysts; it does not ex hibit the high cracking activity of these catalysts even at higher temperatures and accordingly the maximum yield of products is in a higher molecular weight range than in the case of acidic-type hydrocracking catalysts. Further, the catalyst combination tends to give a rnuch wider boilng range spectrum of products than does an acidic-type hydrocracking catalyst. Still further, the maximum total yield of synthetic products, i.e., these products boilng below the inital boilng point of the feed, occurs in a molecular Weight range adjacent to and immediately below the initial boilng point of the feed, whereas in the case of an acidic-type hydrocracking catalyst this maximum yield occurs in a lower boilng range. Clearly, of the multitude of possible compounds in a given feed, many of these compounds must undergo different cracking and other reactions in the presence of the aforesaid non-acidic-type hydrocracking catalyst than they do in the presence of acidic-type hydrocracking catalysts; otherwse, the substantial dfierences in yeld structure obtained with the two types of catalyst could not be accounted for.

A corollary feature of the use of the aforesaid non-acidic or substantially non-acidic-type hydrocrackng catalyst in the process of the present invention is that such a catalyst generally has excellent denitrifieation activity and, where nitrogen is present in the feed to the process, the catalyst efliciently couverts it in the reaction zone te ammonia, which may be removed from the reaction zone effluent by conventional procedures, such as the water scrubbing illustrated in FIGURE 1 hereof. As discussed under Feed to First Conversion Zone above, the nitrogen content of the feed to the first conversion zone is dependent upon the nitrogen content requirements of the feed to the second conversion zone.

The hydrocracking accomplished in the first conversion zone facilitates denitrificaton because, upon the breaking of carbon-to-carbon bonds, nitrogen is more easly removed. At hgher levels of cracking conversion, the nitrogen is more easily removed than at lower levels. At hgher levels of cracking conversion hgher pressures are requred to prevent rapid fouling and deactivation of the catalyst.

The nitrogen compounds tend to concentrate in the heavier portions of the feed; accordingly, such heavier portions as such are more diificult to denitrify. HOW- ever, it will be noted from the foregoing that such heavier portions also are easier to crack in the first conversion zone. Accordngly, the first conversion zone operates to reduce the work load on the catalyst in the second conversion zone and also operates to reduce the nitrogen content of the feed to the second conversion zone, which is a desirable objective.

Partcularly with heavy feeds it may be desirable to operate the first conversion zone in a counterflow man ner, that is with the hydrogen being passed through the first conversion zone in a direction counter to the direction of the feed. Another desirable method of operation may be to operate the first conversion zone as two reaction systems in series with intermediate stripping of H S and NII These types of operation will improve the hydrodenitrification eflciency of the zone.

The first conversion zone is operated at combinations of conditions selected trom within the following ranges that will produce the desired degree of hydrocracking:

p.s..g., more preferably 1000 to 2500 p.s.i.g., and a liquid hourly space velocty of about 0.1 te 3.0, preferably 0.4

to 1.0. The hydrogen flow to the first conversion zone is at least 1000 s.c.f. per barrel of feed,and Preferably 1500 to 6000 s.c.f. perbarrel of feed." The hydrogen partial pressure, of course, willdepend upon a number of factors, including type of feed stock and nitrogen content thereofdegree of der1itrification required, etc.; however, in general a hydrogen partial ptessure of 1000 to 1500 p.s.i.g. is highly desirableif practicable in any given instance. Further, it is desirable that the. hydrogen par- 1 all remaining material boiling above 320 F., the material passed to the second conversion zone may be limited to material boiling above 00 F.

tial pressures in both the first and second conversion Zones be maintained at substantially the same level.

Referrng now to FIGURE 3, theie shown is an exemplary graphical representatonof-the product di stribution obtained when hydrocracking a specific fced stock in the first conversion zone in the presence of a representative catalyst, namely, sulfided nickel-rnolybdenum on alumina. It will be noted from the graph that the feed stock had anitrogencontnt of 1700 parts per million and that, at the operating condtions of S00 F., 1200 p.s.i.ig. and 0.1 LHSV, the fed stock was de1iitrified down to a level of 12 parts per million nittogen. It will also be noted from the graph that the upper curve is the distillation cufveof the feed before being subjcted to hydrocracking and that the lower curve is the distillation curve of the products obt-ained from the hydrocracking.

From the upper curve it is seen that approximately 70 volume percent of the feed boiled above 800 F. From the lower curve it is seen that about volumepercent ofthe products boiled below the initial boilingpint of.

the feed and that the remaining 65 volume percentof the products boiled below the boiling range of approximately 70 volume percent of the feed.

Referring now to FIGURE 4, there shown is an exemplary graphical representation of the feed boiling range on the cracking conversion in the first stageof the process of the present invention. The curve is a plot of the results of hydrocracking various Stocks of various boiling ranges at the identical operatng condtoris of 800 F., 1200 p.s.i.g. and 0.4 LHSV over a catalyst comprising ickel-molybdenum on alumina. It will be seen that the rate of cracking decreases rapidly as the molecular weight of the feed decreases. When cracking.a molecule containing 30 carbon atoms, forexample, once it,is cracked down to 15 carbon.atoms, the chance of it cracking again over the catalyst used in the first conversion zone in the present process is small, whereas in the presence of an acidic-type hydrocracking catalyst it is very lkely to crack again. version zone of the present process produecs a much higher yield of middle distillates from a given feed stock than does the acidic-type catalyst.

INTERSTAGE FRACTIONATION AND CUT POINTS will indicate variations in process operation as influenced by the various boiling points at which cuts maybe made on column 16 and the resultng fractions-subsequently manpulated, whether by being withdrawn as product,

passedto the second conversion zone, or recycled to the first conversion zone.

(1) S0 longas at least a naphthfraction boiling below 400 F. is withdrawn from the system as a product through line 18, all remaining material from column 16 that boils above 320 F. may be passed to the second conversion zone.

(3) The process may be operated as in (1), above,except thatinstead of passing all of the material boiling above 320 F. to the second conversion zone, at least a portion of that material is recycled to the first conversion zone.

(4) The process may be operated as in (1), above, with the additonal feattire of recycling to the second conversion zone atleast a portion of the eflluent therefrom that boils above the initial "boiling point of the feed thei*eto (5) The process may be operated as in (1), above, except that at least a portionof the materials from the interstage fractionation zone boiling above about 320 F. is recycled to the first conversion zone, and with the additional feature of recycling to the second conversion zone at least a portion of the efiluent therefrom that boils above the initial boiling point of the feed thereto.

(6) The process may be operated as in (3), above, but

with the portion of the matrial .recyled from the inter- -terial boiling above about 5 00F.

It will be readily seen from the above pssible types of operationof the process of the present invention that the great vafiety of cut points and types of recycle that may be employed permit the widest flexibility in process Accordingly, the catalyst used in the first conoperation, particlarly in permitting wide variations in the ratio of gasoline to middl distillate production to meet seasonal swings in demand and demand changes for other reasons. It will be noted, particularly in view of FIGURE 2 'berein, that the first conversion zone produces a maximum amount of middledistillates and the second conversion zone produces the maximum amount of prodboiling materials from the interstage fractonation zone to the first conversion zone; and

(2) Gasoline production can be maximizecl by passing to the second conversion zone all eflluent from the fractionation zone boiling above the naphtha boiling range,

and by recycling to the second conversion zone from the eflluent thereof all materials boiling above the naphtha boiling range.

It has been found that at the first of the foregoing extremes the ratio of rrriddle distillates to gasoline production, as a volume percent of the nitial distillate feed, can be quite large, for example 51.7/28.5, while at the second extreme the ratio can be as low as zero.

It is within the purview of the present invention to use a common fractionation zone to handle the efliuent from the first and second conversion zones, rather than using separate fractioriation zones as illustrated in FIGURE 1. These skilled in theart, upon reading the present specification, will be aware of the various factors that will require consicleration in deciding to use a common fractionation zone ratherthantwo fractionation zones, and will be;aware of the possible difierences in process results, includingoperational flexibility and case of product separation involved in the use of two fractionation zones instead of one.

The aforesaid flexibility is further illustrated by the following specific variations in the manner of manipulating the process cut points and recycle streams.

volume percent per pass of the feed thereto to products boiling below the intal boiling point of said feed.

While some nitrogen can be tolerated in the second T abl e 1 Recyclc to first Net product removed Feed to second Recyole to second conversion zone trom interstage convers1on zone converslon zone Purpose fractionatlon zone (A) None Below 300 to 400 F...-- Above 300 to 400 F Above 300120 400 F. Maximize gasoline production.

(B) None (C) Above 600 te 900 F.-

(D) Above 600 to 900 F-..

Below 500 to 800 F Below 500 to 800 F..

Below 300 to 400 I.

Below 300to 600 F. and

Above 500 to 800 F 500-800 F. to 600 900 F-..

300 400 F. to 650900 F...

Between 300 to 600 F.

Above 500 te 800 F Above 500 to 800 I.

Above 300 to 400 F.

Above 300130 600 F.

Produee gasolne and middle distillates.

Maximize rniddle dstillates with recycle to first coversion zone.

Mmrmize gasolne with reeyole to rst converslon zone.

Matlmize gasolinc production, whle (E) None above 600 to 800 F.

and 600 to 800 F.

removing trom system heavy product trom first oonverslon zone.

FEED TO SECOND CONVERSION ZONE The foregoing discussion of the feed to the first conversion zone and of the varions possible inter-stage fractonaton cut points and methods of product removal and recycle, together with the previous discussion of nitrogen contents, adequately defines the eed to the second conversion zone.

SECOND CONVERSION ZONE The catalyst in the second conversion zone comprises a hydr0genating-dehydnogenating component and an active acidic cracking component. In the light of the present disclosure, those sklled in the art will be able to select specific catalysts suitable for the particular instances with whch they are concerned. For purposes of the present invention, it will be suflcient if any of the well-known solid active acidic cracking components used for hydrocracking are selected, including silica-alumina, activated alumina, alumina-BF combnations, and varous fluorided or selenided catalyst supports. The hydrogenating-dehydrogenatng component may comprise at least one metal, metal oxide, metal sulfide, metal selenide, or combination thereof, preferably selected frorn metals of Group VII and compounds thereof, including nckel, platinum and palladium and compounds thereof. As in the case of first stage catalyst, the second stage catalyst is preferably prepared by irnpregnation, but various cogelation procedures are fully operable. ferred catalyst composite of Scott U.S. Patent No. 2,944,- 006 will be especially suitable in the process of the present invention. A very desirable method of operatng the second conversion zone is to recycle to that zone a hydrogen-rich gas stream trom which ammonia has been removed. As discussed above, varous hydrocarbon fractions may be recycled to the second conversion zone. The product fractions from the second conversion zone that boil below the initial boiling point of the feed constitute excellent gasoline blending stocks for certain purposes; however, where they are desired for gasoline purposes, t will generally be found more desirable to send at least the heavier portons of them to a catalytic reformer where they will serve as a most excellent preferred feed for catalytic reforming operations.

The second conversion zone is supplied with at least 1500 s.c.f. of hydrogen per barrel of feed thereto. At least 500, and normally from about 1000 to 2000 s.c.f. of hydrogen are consumed in the second converson zone per barrel of feed thereto that is converted to synthetc products, i.e. prodncts bolling below the initial boiling point of the feed thereto.

Operating conditions in the second conversion zone will include a temperature of 450 to 850 F. preferably 500 to 800 F., a liquid hourly space velocity of 0.2 te 5.0, preferably 0.4 te 3.0, and a hydr=ogen partial pressure of at least 350 p.s.i.g. preferably 500 to 2000 p.s.i.g. In the second converson zone there is converted at least conversion zone, as discussed above, nitrogen is an undesrable ngredient of the feed thereto and should be kopt wthin the aforementioned limits.

EXAMPLES EXAMPLE NO. 1

Feed: 650-800" F. Arabian gas 011 Gasoline cut point: 400 F.

Reeycle (2nd stage) cut point: 650 F. Yields, first stage leed basis:

Conventional Process of process present invention Weight percent C;C 2.1 2.0 Weight percent 1-C4 6. 5 5.9 Weight percent n-C 2. 2 2.0 U LV percent 05400 F. gasoln0 76 67 LV percent 400650 I. middle distlllate:

First stage 0 16 Second stage 30 22 Total, 400-650" F 30 38 Middle distlllate/gasoline 0. 395 0. 568

The ent1re pre- EXAMPLE 2 Feed: 510800 F. California heavy cycle oil Gasoline eut pont: 320 I. Reoyele out point (2nd stage): 510 F.

Yields, first stage leed basis:

Conventional Process of process present nvention Weight percent C;C; 1. 5 1. 8 Weight percent i-C4.... 5. 6 6. 0 Weght percent n-C; 1. 1 1. 6 LV percent 05-180 I. gasoline. 21 22 LV percent 180320 F. gasoline 57 44 LV percent 320-510 F. middle dstillate:

60 F.rst stage. 0 20 Second stage- 37 26 Total, 320510 F 37 46 Middle d.istlllatelgasolne 0. 475 0. 695

COMBINATIONS WITH OTHER CONVERSIN PROCESSES As discussed above in connection wth FIGURE 1, there may be withdrawn from the system through lines 33 and 49 either net product strearns or feed streams for catalytic cracking. A particularly excellent catalytic feed stock is so obtained when a heavy gas oil 01 heavy cycle oil feed is supplied to the first conversion zone, and the 650 F. and heaver portions of the efluent therefrorn are sent to catalytic cracking. Any naphtha stream ent invention is an excellent reformer feed stock.

CONCLUSION From the foregoing it may beseen that the novel methods of the present invention are eective in providing a large degree of operatinal flexibility in the:type of two-stage hydrocrackng process to which the inventon relates, and are efi'ective in accomplishing the prduction of superior products, including diesel fuels and jet fuels.

Although only specific arrangements and modes of operation of the present invention have been described and illustrated, numerous changes could be made in these arrangements and modes without departng from the spirit of the invention, and all such changes chat fall within the scope of the appended claims are intended to be embraced thereby.

1. In a two-stage process for producing valuable fuel products from a hydrocarbon feed selected from the group Consistng of hydrdcarbon dstillates having an initial boiling point ofat least 500? F. and an end point below about 1100 F. and hydrocarbon residua boiling above about 1050 F., which comprises. converting in a first conversion zone from 10 to50vol. percentof said feed per pass to fractions boiling below the initial boiling point of said feed, said first zone beng opetted at about550 900 F. a space velocity from about 0.13.0 and a hydrogen partal pressure of 1000-2500 p.s.i.g. withdrawing an effluent fromsad first zone, separating said efiuent into fractions in a separaton zone, withdrawing from said separation zone at least one of said fractions as a product,

converting in a second conversori Zonet leat"i1e f saidfractions at a conversion of at least 20 vol. percent per pass to products boiling below the intia l boiling point of said fracton passedto said second zone;said second zone being perated at about 45 850.F. a space velocity from about 0.25.0 and a hydrogenpartial pressure of at least 350 p.s.i.g. with a catalyst comprising a hydrogenating-dehydrogenating component andan actve acidic cracking component, withdrawing a11 effluent from said second zone and recoverng the desiredproducts from said eflluent, the improvement whch comprises:

naphths, heating oils,.

12 (a) usingas the catalyst in said first zone a catalyst comprisng 4-10 wt. percent of-a component selected from the group cons isting of nickel and compounds thereof, and 15.5-30 wt. peicentof a component se- 5 lected from the group consisting of molybdenum and compounds thereof and a substantially non-acidic component essentally of alurnna,

(b) wthdrawing from said separation-zone. a naphtha fracton boiling between C and 400 F., a middle distillate fracton boi1ng between about -400 and 650 F., and a bottoms fracton boiling above about 650 F.

(c) recovering said naphtha fracton as a product,

(d) recoverng a porton of said middle dstillate fracton as a product,

(e) passing at least a portion of said bottoms fracton and the remainder of said middledistllate fracton to said second zone, said feed to said second zone beng passed through the entire catalyst bed in said second zone, and

(f) recycling to said second zone at least a portion of said effluent from said second zoneboilingabove the initial boiling point of said feed to said second zone;

- 2; A process as in claim 1 Wherein at least a porton of the effluent from said separation zoneboilng above about 400 F. isrecycled to said first zone.

3. A process asin claim 1 wheren at least a portion ofsaid fracton boiling above about 650 F. from.said 30 firstzone is passed to a satalytic cracking zone.

4. A process asin claim 1 wherein at least a portion of said effluent from said second zone boiling above about 650 P. is passed to a catalytic crackng zone.

References Cited by theExaminer UNITED STATES PATENTS ALPHONSO D; SULLIVAN, Prz'mary Examiner[ PAUL M. COUGHLAN, Examz'ner. 

1. IN A TWO-STAGE PROCESS FOR PRODUCING VALUABLE FUEL PRODUCTS FROM A HYDROCARBON FEEL SELECTED FROM THE GROUP CONSISTING OF HYDROCARBON DISTILLATES HAVING AN INITIAL BOILING POINT OF AT LEAST 500*F. AND AN END POINT BELOW ABOUT 1100*F. AND HYDROCARBON RESIDUA BOILING ABOVE ABOUT 1050*F., WHICH COMPRISES CONVERTING IN A FIRST CONVERSION ZONE FROM 10 TO 50 VOL. PERCENT OF SAID FEED PER PASS TO FRACTIONS BOILING BELOW THE INITIAL BOILING POINT OF SAID FEED, SAID FIRST ZONE BEING OPERATED AT ABOUT 550*900*F., A SPACE VELOCITY FROM ABOUT 0.1-3.0 AND A HYDROGEN PARTIAL PRESSURE OF 1000-2500 P.S.I.G., WITHDRAWING AN EFFLUENT FROM SAID FIRST ZONE, SEPARATING SAID EFFLUENT INTO FRACTIONS IN A SEPARATION ZONE, WITHDRAWING FROM SAID SEPARATION ZONE AT LEAST ONE OF SAID FRACTIONS AS A PRODUCT, CONVERTING IN A SECOND CONVERSION ZONE AT LEAST ONE OF SAID FRACTIONS AT A CONVERSION OF AT LEAST 20 VOL. PERCENT PER PASS TO PRODUCTS BOILING BELOW THE INITIAL BOILING POINT OF SAID FRACTION PASSED TO SAID SECOND ZONE, SAID SECOND ZONE BEING OPERATED AT ABOUT 450*-850*F., A SPACE VELOCITY FROM ABOUT 0.2-5.0 AND A HYDROGEN PARTIAL PRESSURE OF AT LEAST 350 P.S.I.G. WITH A CATALYST COMPRISING A HYDROGENATING-DEHYDROGENATING COMPONENT AND AN ACTIVE ACIDIC CRACKING COMPONENT, WITHDRAWING AN EFFLUENT FROM SAID SECOND ZONE AND RECOVERING THE DESIRED PRODUCTS FROM SAID EFFLUENT, THE IMPROVEMENT WHICH COMPRISES: (A) USING AS THE CATALYST IN SAID FIRST ZONE A CATALYST COMPRISING 4-10 WT. PERCENT OF A COMPONENT SELECTED FROM THE GROUP CONSISTING OF NICKEL AND COMPOUNDS THEREOF, AND 15.5-30 WT. PERCENT OF A COMPONENT SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM AND COMPOUNDS THEREOF AND A SUBSTANTIALLY NON-ACIDIC COMPONENT ESSENTIALLY OF ALUMINA, (B) WITHDRAWING FROM SAID SEPARATION ZONE A NAPHTHA FRACTION BOILING BETWEEN C5 AND 400*F., A MIDDLE DISTILLATE FRACTION BOILING BETWEEN ABOUT 400* AND 650*F., AND A BOTTOMS FRACTION BOILING ABOVE ABOUT 650*F., (C) RECOVERING SAID NAPHTHA FRACTION AS A PRODUCT, (D) RECOVERING A PORTION OF SAID MIDDLE DISTILLATE FRACTION AS A PRODUCT, (E) PASSING AT LEAST A PORTION OF SAID BOTTOMS FRACTION AND THE REMAINDER OF SAID MIDDLE DISTILLATE FRACTION TO SAID SECOND ZONE, SAID FEED TO SAID SECOND ZONE BEING PASSED THROUGH THE ENTIRE CATALYST BED IN SAID SECOND ZONE, AND (F) RECYCLING TO SAID SECOND ZONE AT LEAST A PORTION OF SAID EFFLUENT FROM SAID SECOND ZONE BOILING ABOVE THE INITIAL BOILING POINT OF SAID FEED TO SAID SECOND ZONE. 